Optical coherence tomography imaging

ABSTRACT

A digitized image of an object may include representations of portions of the object that are obscured, occluded or otherwise unobservable. The image may be a multi-dimensional visual representation of dentition. Characteristics of the dentition and its surfaces, contours, and shape may be determined and/or analyzed. A light may be directed toward and reflected from the dentition. The reflected light may be combined with a reference to determine characteristics of the dentition, including obscured areas such as subgingival tissue.

PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to provisionalapplication No. 60/468,759, filed on May 5, 2003, entitled a DentalImaging Device and System, the disclosure of which is incorporated inits entirety herein by reference.

BACKGROUND OF THE INVENTION

1. Related Field

The invention relates to the imaging of tangible objects, and inparticular to multi-dimensional imaging of tangible objects.

2. Description of the Related Art

Some imaging technology use a triangulation technique to image anobject. Imaging technologies may be used in dentistry for bothintra-oral and extra-oral applications. While triangulation may bereliable and effective to image dental models, in some circumstances,reflections from translucent dentition may lessen the perception of anobject.

Intra-oral imaging systems may also be susceptible to operator movement.A movement may affect the system's ability to capture an accuratedepiction of an object. Intra-oral imaging systems also may have limitedability to capture dentition above the gum line. Intra-oral imagingsystems may not capture images of internal, underlying, or occludedstructures such as portions of dentition that are in close proximity tocontiguous or nearby dentition or obscured by gingival and/or tartar.

SUMMARY OF THE INVENTION

An Optical Coherence Tomography (OCT) imaging embodiment may digitize orcapture visual images of tangible objects. The embodiments may digitizethe tangible objects, or portions thereof, including areas of theobjects that may be obscured and/or occluded.

An OCT imaging embodiment may generate one-, two-, three-, or othermulti-dimensional images, or visual representations, of an object. Theimages may outline multi-dimensional surfaces, structures, contours, andother forms sizes, distances, and/or colors of the object that areobstructed. The object may include intra-oral dentition and extra-oraldental models.

An OCT imaging embodiment may include a broadband light source, areference arm, a projector, a coupler, a sensor, and a processor. Thebroadband light source may generate a structured light that is projectedtoward an object. The structured light may be provided to the referencearm, which generates a reference beam using the structured light. Lightreflected from the object and the reference beam may be combined at thecoupler to create a superimposed interference pattern. The interferencepattern may be detected by a sensor which that generates signalsrepresentative of superimposed interference pattern. Using an inputsignal, the processor may generate a dataset representative of thecharacteristics of the object. The dataset may be used to generate amulti-dimensional image of the object and may include image enhancementand data compression. The dataset may be used to form a model of theobject. The processor may also analyze, manipulate, store or furtherprocess the dataset based on time domain analysis, Fourier Domainanalysis (also known as Spectral Domain analysis) or a combination oftime domain and Fourier domain analysis.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIG. 1 illustrates an optical coherence tomography (“OCT”) imagingembodiment.

FIG. 2 illustrates a projector of an OCT imaging embodiment of FIG. 1.

FIG. 3 illustrates a Time domain OCT imaging embodiment.

FIG. 4 illustrates a Fourier domain OCT imaging embodiment.

FIG. 5 illustrates a light projection of the OCT imaging embodiment ofFIG. 1.

FIG. 6 illustrates a light projection the OCT imaging embodiment of FIG.1.

FIG. 7 illustrates an OCT embodiment digitizing a preparation.

FIG. 8 illustrates an OCT embodiment for detecting a margin.

DETAILED DESCRIPTION OF THE INVENTION

An optical Coherence Tomography (“OCT”) embodiment may capture images ofan object. The images may include portions of the object that are notvisible, obscured, occluded or otherwise not observable by a line ofsight. The object may be an intra-oral tissue or one or more dentalitems, such as a tooth, multiple teeth, one or more preparations, one ormore restorations or a dental arch, for example.

An OCT imaging embodiment may identify faults and voids on an interiorportion of a tooth, may detect decay of interior portions of dentition,and may detect the presence and/or extent of sub-gingival tartar. Theimages captured by an OCT imaging embodiment may verify presence anddegree of tooth damage such as cracks and assist in the preparation ofdental procedures, including root canals. The images of obscured areasmay reduce or eliminate invasive procedures that require removal oftissue to view or inspect the obscured areas.

FIG. 1 illustrates an exemplary OCT imaging system 100. The OCT imagingsystem 100 may include a light source 102, an optical coupler or beamsplitter 104, a reference arm 106, a projector 108, and a sensor 110.The OCT imaging system 100 also may be coupled to a processor (not shownin FIG. 1).

The light source 102 may convert incident electromagnetic radiation ofmultiple frequencies to a coherent visible of invisible beam of light.The light source 102 may be a broadband device such as an LED orsemiconductor pumped laser source such as a laser diode. The light maycomprise constituent wavelength or one or more frequencies of coherentlight. The constituent wavelengths of the light may lie in the range ofabout 600 to about 1700 nm. In one embodiment, the constituentwavelengths may lie the range of about 600 to about 900 nm. In analternative embodiment, the wavelengths may lie in the range of about1100 to about 1700 nm. In another embodiment, the wavelengths may be inthe infra-red region. In yet another embodiment the wavelengths are inthe range of visible light.

The light may pass through or be guided by various optical devices. Theoptical devices may scan, focus, polarize, expand, split, and/or directthe beam of light. The optical components may generate a structuredlight pattern. In an embodiment, the optical devices may generate afocused beam or dot light that may be moved or scanned along astructured pattern. The optical devices may include mirrors, lenses,relays, guides, splitters, gratings, scanners, polarizers etc. andcombinations of these devices.

The optical coupler (beam splitter) 104 may be coupled to the lightsource 102 through an optical instrument. The optical coupler 104 may beoptically coupled to the light source 102 through an optic cable, anoptical guide wire, an optical relay, free-space optics, and any otherlight transmitting technology, or any combination thereof. The opticalcoupler 104 may also be a unitary part of the light source 102.

The optical coupler. 104 may separate, divide or split the structuredlight into multiple paths. In an embodiment, the optical coupler 104splits the structured light into two or more paths that include a firstoptical path 120 and a second optical path 122. The first optical path120 and the second optical path 122 may include various lighttransmitting instruments or devices that guide the structured light to adestination. In one embodiment, the first optical path 120 and thesecond optical path 122 may be strands of transparent material, suchspecial types of glass and plastics that carry optical signals. It mayalso include optical fibers, a bundled fiber optic cable, an opticalguide wire, an optical relay, free-space optics, or any one orcombination thereof. The first optical path 120 guides the light to thereference arm 106. The second optical path 122 guides the light to theprojector 108.

The reference arm 106 may receive the light through the first opticalpath 122 and reflect the light toward the coupler 104. The lightreflected from the reference arm 106 may return to the coupler 104through the first optical path 120. A reference arm 106 may include alight path having an optical fiber optically coupled to a collimator orfocusing optics and a mirror. The light path directs the light to themirror, which may reflect the light along the light path.

The reflected light through the light path may include most of theconstituent components of the structured light from the light source102. The light may be substantially unaffected or altered by referencearm 106 or the coupler 104. A baseline measurement of the traveleddistance of each of the constituent components of the light may bemeasured. The baseline measurement may provide a reference for ameasurement of traveled distance of the reflected light. The baselinemeasurement may be compared with the distances other light originatingfrom the light source 102 passes through media other than air maytravel, such as the distance light reflected from the object 112 maytravel. The comparison may include superimposing the baselinemeasurement of the light returned from the reference arm 106 with anyother light reflected from the object 112. Based on an interferencepattern of the superimposition, a distance traveled by the reflectedlight may be determined. For example, a known distance between the lighttraveling through reference arm 106 and returned to the coupler 104 maybe equal to a distance traveled by any other light returned to thecoupler and combined with the reflected light. Variations may bedetected to determine surface characteristics of the object 112.

The projector 108 may be coupled to the coupler through a second opticalpath 122. The projector 108 may be portable and/or handheld. Theprojector may be manipulated or inserted into an oral cavity. Theprojector 108 may focus or otherwise direct structured light 124 towardan object 112. The projector 108 may project the beam of light 124toward the object 112 in a varied or structured pattern. The light 124may converge all or a portion of the object 112. The light 124 also maybe focused on structures that prevent the light from illuminating theobject 112. For example, if the object 112 is a tooth and the light 124may be so that a light pattern is projected onto the tooth. The light124 also may be directed toward gum tissue surrounding or near asub-gingival portion of the tooth. The pattern may be projected on thetooth, the gum tissue, or any part or combination of the oral cavity.The beam of light 124 may be direct towards the dentition so that thestructured pattern is reflected therefrom.

The projector 108 may also detect the light reflected from the object112. The reflected light may be directed along a return path to thecoupler 104. The return path may be substantially parallel to the firstoptical path 122. The return path may also coincide with the firstoptical path 122 in a reverse direction.

The reflected light may strike the surface of the coupler. The coupler104 may combine the reflected light with light returned from thereference arm 106. When the combined lights interfere with each other,the interference may create a superimposed interference light pattern.The superimposed light pattern may detect a shape, distribution andcomposition that represent surface characteristics of the object 112.The surface characteristics may include both exterior surfaces andinterior surfaces. The surface characteristics also may includecharacteristics of surfaces that are obscured, occluded or otherwisehidden from a normal view.

The surface characteristics may be identified by detecting differencesin color, shading, intensity and distance through reflections ofportions of the light from the surface of the object 112. In oneembodiment, the light reflected from the reference arm 106 and the lightreflected from the object 112 may originate from light source 102. Theconstituent components of the light reflected from the reference arm 106may be substantially similar to the respective components of the sourcedlight. The distance traveled by the light within the reference arm 106may be known or predetermined and provide a baseline used to render animage. The baseline may include the constituent components of the sourcelight and the distance traveled by the source light.

The reflected light may be reflected from an exterior surface of theobject 112. The light may also penetrate the surface of the object 112and be reflected from an interior surface of the object 112. Forexample, a portion of the light may be reflected from the exteriorsurface of the object and a portion of the light may be reflected fromas an interface between materials within the object 112, or from anoccluded surface. Constituent components of the source light may bereflected or absorbed, based on properties of the object including anyconstituent materials, and interfaces between materials of the object112. The reflected light from the object 112 may include constituentparts of the original sourced light or may be substantially differentfrom the original sourced light. In addition, the light reflected fromthe object may be reflected from different distances within the object.For example, a constituent set of reflections from the object maycontain constituent components that may occur at an air/gum interface,and another constituent set of reflections may be created by agum/enamel interface.

The light reflections from various portions of the object 112 may becombined or superimposed with the baseline light at the coupler 104. Bycombining or superimposing the baseline light with the light reflectedfrom the object 112 or its various surfaces, an interference may bedetected. The interference properties may be provide a comparison of thebaseline and the light reflected from the object 112. With the distancetraveled by the light by the reference arm 106 known, the distance eachreflection travels from a surface may be determined.

Since the baseline measurement includes a distribution of theconstituent components of the source light 102, a type of interface ateach surface on and within the object 112 may be determined based on theconstituent components of the source light that are absorbed orreflected at each interface. The degree to which each interface betweendifferent materials absorbs, reflects or transmits a constituentcomponent of the source light may depend on properties of the materialand the interaction of light with the material. For each position of thelight beam incident upon the object, a dataset may be determined. Thedataset may be generated to represent a visual representation of theobject 112.

The superimposed interference light pattern may be directed by theoptical coupler 104 to the sensor 110. The sensor 110 may capture and insome embodiments may digitize the superimposed interference lightpattern to generate signals that represents the shape, distribution,color, shading, and/or composition of the superimposed interferencelight pattern or any combination thereof.

The signals from the sensor 110 may be processed by a processor or acontroller. The processor may generate a dataset that represents variouscharacteristics of the object 112 and/or its surfaces, such as itsshape, height, width, contour, and exterior arrangement, and the volumeetc. The processor may use time domain or frequency domain analysis suchas Fourier domain data processing. The processor may also include animage enhancement application that may improve the quality of thecaptured image automatically through software or manually by a userprogram.

FIG. 2 illustrates an exemplary projector 108. A first optical path 122guides the light from a light source 102 to the projector 108. Theprojector 108 may include a focusing or collimating element 132 thatdirects the beam of light 115 to a scanner 134.

The scanner 134 may include one or more reflective surfaces 136. Thereflective may surfaces scan the beam of light 115 along multiple axes.The scanner 420 may be a one-, two-, three-, or other multi-axisscanner. One example of a scanner 420 is described in co-owned U.S.patent application Ser. No. ______, filed on Mar. 19, 2004, entitledLASER DIGITIZER SYSTEM FOR DENTAL APPLICATIONS and referenced byattorney docket number 12075/37. The disclosure of the aforementionedco-owned US patent application is incorporated by reference in itsentirety herein. The directed beam of light 138 exits the scanner 134and may be incident on a first prism 119 that bends or changes thedirection or path of the light 138. The first prism may direct the beamof light to a relay 140. The relay 140 may be a rod or GRIN (gradientindex) lens. The beam may be focused by an objective focusing element142, and may be deflected toward the object 112 through the second prism144. The light is incident upon the object 112. The light is projectedalong a path across the object 112.

The light may project a dot on the object 112 in discrete time. The dotmay be scanned in a one-, two-, three, or other multi-dimensionalpatterns across the object 112. The incident light may be projected to asurface of the object that is obscured, occluded or otherwise notvisible. The light may also be reflected from an interior surface of theobject 112. Portions of the incident light may be reflected back towardthe projector 108 and guided along a parallel optical path as thesourced light. Portions of the incident light may be guided in a reversedirection along the same optical path as the incident light.

FIG. 3 illustrates an exemplary time domain OCT imaging system 300. Thetime domain OCT imaging system 300 may include a light source 302, acoupler 304, a projector 308, a time domain reference arm 306, and asensor 310. The light source 302, the coupler 304 and the projector 308may be similar to the light source 102, the coupler 104, and projector108, respectively, described above.

The time domain reference arm 306 may be generate a time-varying pathlength 310 on which light from the coupler 104 may travel and bereturned to the coupler 104. The time-varying path 310 creates reflectedlight that may be returned to the coupler 304 along a first optical path220. The time-varying time domain reference arm 306 provides a timedependent delayed reference signal having a time delay with respect tothe light transmitted from the source 102. The time-dependent delay maybe based on a time of flight to the time domain reference arm 306 andalong a return path. For example, the time-dependent delay may be basedon a time the light travels from the coupler 304 to a reference mirrorand is reflected back from the reference mirror to the coupler 304. Thetime delayed signal may be used as a reference signal that hassubstantially similar characteristics to the light from transmitted fromthe light source 302, but being delayed in time. An example of thetime-varying path length is a length of optical cable connected to acollimator or focusing optics which images the light onto a moveablemirror that reflects the light back along the same optical cable.

The coupler 304 may combine the time-varying pattern with the reflectedlight from the object 112. When combined with the light reflected fromthe object 112, the combined pattern provides an interference patternthat represents the superimposition of the time-delayed referencesignal. By combining the time-varying reflected light from thetime-varying path length 310 with the light reflected from the object112, the coupler may create an interference pattern that represents adepth, color or shading of the light reflected from the surface andinternal structure of the object 112. The characteristics of the surfaceof the object 112 may be deduced based on differences in shape, color,shading, amplitude, position, features and other attributes that may bedetected by the interference pattern. Similarly, a volume of the object112 may be detected by the shape, amplitude, position and othercharacteristics within the interference pattern. Based on the depth oflight reflected, the height of the object may be determined.

The sensor 310 that detects or measures light by converting it into anoptical or electrical signal may sense the combined interference patternfrom the coupler 304. The sensor 310 may generate analog or digitalsignals that represent the amplitude (or strength) of the interferencegenerated from a combined reflected light from the time-varying path andthe reflected light from the object 112. The sensor 310 may include aphotodetector such as an array of a Charge-Coupled Devices (CCD). Insome embodiments, the sensor may also include a bandpass filter, anenvelope detector, and analog-to-digital converter that generatediscrete signals that represent the distance traveled by light reflectedfrom the object 112.

The processor 314 may generate a dataset representing the varioussurfaces, contours, arrangement, shape and/or size of the object 112based on the signals received from the sensor 310. The dataset may beused to display or print a visual representation or image of the object112. For example, the image may be rendered on a video monitor, or otherdisplay using geometric modeling using colors and shading to give theimage a realistic appearance. Similarly, the image may be transmitted toa head-mounted display that holds the image in front of the user. Anexample of a head-mounted display is described in co-owned applicationentitled Intra-Oral Imaging System, filed on Apr. 30, 2004, andreferenced by attorney docket number 12075/41. The description of theaforementioned application is incorporated by reference herein in itsentirety. The dataset also may be used by a geometric modeling programsuch as a milling program or a CAM program, to render a physical modelof the object 112.

FIG. 4 illustrates an embodiment of a Fourier domain OCT imaging system400 (also referred to as Spectral domain OCT imaging or Fast Fourierdomain imaging). The Fourier domain OCT imaging system 400 may include alight source 402, a coupler 404, a projector 408, a fixed reference arm406, and a sensor 410. The light source 402, the coupler 404 and theprojector 408 may be similar to the light source 102, the coupler 104,and projector 108, respectively, described above.

The fixed reference arm 406 may include a fixed reflecting surface. Thereflective surface may be one or more mirrors that reflect the lightalong a fixed path length. The fixed reference arm 406 may be a fixedlength wave guide optically coupled to the coupler at one end and havinga reflective surface at another end. The fixed reference arm 406 mayalso be a time-varying reference or delay as previously described.

The sensor 410 may include a spectrometer 418 that measures wavelengthsor indices of refraction and a photosensor 416. The sensor 410 mayreceive the combined light from the coupler 404. The spectrometer 418may include a grating that separates the combined light into variousconstituent components, providing a spectrograph of the combined light.The spectrograph may include various frequency components of thecombined light spatially separated within a single image that constitutefrequency data. Each of the constituent components may correspond todifferent wavelength or frequency of light that comprise the broadbandlight source 402. The constituent components may be in differentproportions to the respective constituent components of the broadbandlight source 402.

The photosensor 416 may be an array of light sensitive devices, such asa CCD or CMOS or a linear array. The spectrograph from the spectrometer418 may describe surface characteristics of the object 412. For a givenpoint, a height of the object may be determined based on thespectrograph of a combined light. As the dot may be scanned across thesurface of the object 412, height and position measurements may bemeasured by the photosensor. The photosensor 416 may generate signalsbased on the spectrograph produced by a grating.

A processor or controller 414 translates these signals to datasets thatrepresent the characteristics of the object 112. The processor maygenerate a dataset according through an inverse Fourier Transform suchas an inverse Fast Fourier Transform performed on the data collectedfrom the spectrograph. Based on the inverse Fourier Transform thefrequency data is translated from the frequency domain into the spatialdomain. The frequency distribution of the spectrograph from thespectrometer 418 may generate a spatial distribution according to theinverse Fourier Transformation that may include artifacts. The artifactsmay be spikes that correspond to a spatial position of surfaces alongthe axis of the light projected toward the object 412. Amulti-dimensional location of the various surfaces may be determinedbased on the projected beam toward the object 112.

FIG. 5 illustrates a projection of a beam of light 520 in an X-Z plane.The beam 520 may be projected from the OCT imaging system 501. The beam520 may be incident an interior or exterior area 522 of the object 550.The beam 520 also may be reflected along a common incident path 520.

From a superimposition of the reflected beam returned along the commonpath 520 and light from the interferometer a distance R to the surfacearea 522 along the beam may be determined. The surface area 522 detectedmay be on the first exterior surface of the object 550. In thisembodiment, the beam 520 exits the OCT imaging system 501 at a distancex₀ along the X-axis in the X-Z plane from the optical axis 510 of theOCT imaging system 510. The beam 520 exits the OCT imaging system 501 atan angle φ to the vertical axis 512 parallel to the Z-axis. Together,the parameters x₀ and φ and the projection of R in the X-Z planecharacterize the location of the point 522 in the X-Z plane.

FIG. 6 illustrates the configuration viewed from a perspective in theY-Z plane. The beam 520 exits the OCT imaging system 501 at a positiony₀ along a Y axis from an optical axis 510, at an angle θ to a verticalaxis 612 parallel to the Z axis.

The parameters x₀, y₀, θ, φ and R may be used to determine a location ofthe position 522 relative to a point 511 on the optical axis of the OCTimaging system 501. In this embodiment, the reference point 511 is aportion of the projector. The parameters x₀, y₀, θ, φ may be determinedbased on the position of the components in the projector, such as therotational parameters of a two axis scanner. The parameters x₀, y₀, θ, φmay be determined by a calibration procedure or by some othermeasurement procedure. The parameters x₀, y₀, θ, φ may be uniquelydetermined by the orientation of the reflective surfaces in the scanner,and the fixed geometric dimensions of the OCT imaging system. Thedistance R may be correlated to the superimposed interference pattern ofthe combined. The distance R may be a measurement along the path 520,and include X, Y or Z components of the surface area 522.

The path 520 does not have to be located completely within the X-Z orY-Z planes. Where the position of the point 522 on the surface of theobject being imaged is (x_(i), y_(i), z_(i)), the coordinates x_(i),y_(i), and z_(i) may be determined according to the parameters x₀, y₀,θ, φ and R as follows:xi=R cos θ sin φ+x 0  eq. 1yi=R cos θ sin φ+y 0  eq. 2zi={square root}{square root over (R ² −((xi−x0) ² +(yi−y0) ² ))}  eq. 3The processor may be configured to determine the coordinates x_(i),y_(i), and z_(i) based on the above parameters using these equations.

FIG. 7 illustrates an embodiment of the OCT imaging device that maydigitize a prepared tooth or preparation 730. A beam of light mayconverge through by an axis 710. The beam may be projected along theaxis 710 to strike a surface of a preparation 730 and a neighboringtooth 720. The beam may be incident upon a surface of the neighboringtooth at a neighboring area 712 along an axis of the beam 710. Portionsof the light incident at the neighboring surface area 712 may reflectback to the OCT imaging device along the same axis 710. Remainingportions of the light may pass beyond or penetrate the neighboring tooth720, exit the neighboring tooth 720 and enter gingival tissue 740.Portions of the light may reflect back from the both the interfacebetween the neighboring surface area 712 and the gingival tissue at 714along the axis 710. Remaining portions of the incident light maycontinue along the axis 710 and may be incident upon the surface of theprepared tooth 730. Portions of the light may be reflected from a marginarea 716 of the preparation 730.

The reflected light detected along the axis 710 may be analyzed todetermine a position of the various surfaces areas 712, 714 and 716. Athree dimensional representation, map or image of the surface of theprepared tooth 730 may be generated from a collection of determinedsurface areas. An image of the margin area 716 may be determined even ifa direct view from the OCT imaging device may be occluded by neighboringdentition, other tissue or material.

Additional internal structures within the tooth such as dentin component725 may also be detected. Tartar or decay present may also be detected.Various surfaces may have a unique signature in the analysis of thecombined interference pattern and therefore the various surfaces may beimaged.

The surface area 712 may be an air/enamel interface with a uniquedistribution of reflected light. An interface area 714 may be anenamel/gingiva interface with a unique distribution of reflected light.An interface area 716 may be a gingiva/enamel interface with a uniquedistribution of reflected light. If a signal is detected that has thecorrect form and shape and strength of typical signal of light reflectedfrom an air-enamel interface, the distance R may be determined based ona measurement of the reference path length of the reference arm pathdistance at the particular position which caused the signal.

FIG. 8 illustrates an embodiment of an OCT imaging device fordigitization of a shoulder or marginal ridge of a prepared tooth 830. Abeam of light may be projected along the axis 810 toward the tooth 830.The beam may be incident on the prepared tooth 830 at a point above amarginal ridge 816. A portion of the light may be reflected from thesurface 816 and returned along the axis 810 to the OCT imaging device.Other portions of the light may penetrate the surface area 816 andcontinue along the axis 810 through the prepared tooth 830. Otherportions of the light may exit the prepared tooth beyond marginal ridgeat the area 818. The light may also be reflected from the surface area818. The reflected light may be analyzed to determine the location ofthe points above and below the marginal ridge. An intersection point ofthe surfaces above and below the marginal ridge may be determined, andprovide an accurate margin measurement. This may be extended to thedetection of various features which can be approximated as anintersection of two or more surfaces.

In another embodiment, an OCT imaging device may digitize dental moldsor castings. The molds or castings may be a material that is transparentto an operating wavelength of the OCT imaging system. The surfaces ofthe mold not directly accessible to the OCT imaging system may bedigitized by capturing images through the transparent material.

In another embodiment, an OCT imaging system non-invasively measurespresence and/or amount of sub-gingival tartar. The OCT imaging systemmay measure a two-dimensional region through existing gingival tissue todetect tartar presence. The OCT imaging system also may measure a two-,three-, or multi-dimensional regions.

In another embodiment, a surface may be inferred by assuming smoothnessof the surface locally from where surface data is available. This mayoccur using one-, two- or three- or other multi-dimensionalinterpolation techniques. For example, a bicubic or NURBS (Non UniformRational B-Spline Surface) patch may be fitted to a local surface, inorder to infer the data that may be missing from the surface. Gaps inthe surface data may be inferred via interpolation techniques as knownby those experienced in the art.

A three dimensional model provided by an OCT imaging embodiment may havefar ranging applications, including application in preventativedentistry, preventative diagnostic procedures, detection of gumretention, detection of tartar, and fitting and formation ofrestorations such as crowns bridges, onlays, inlays and other dentalrestorations, orthodontics, periodontal analysis, retainers and thelike.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents.

1. An intra-oral digitizer, comprising: a light source configured togenerate a beam of structured light having constituent components; areference arm configured to generate a reference beam of light based onthe beam of structured light; a projector configured to project the beamof structured light toward an object and to detect a reflection of atleast a portion of the beam from a at least a surface of the object, thebeam being projected toward the object as a dot that traverses a patternacross the surface of the object; a coupler configured to combine thereference beam and the reflection to generate a superimposedinterference light pattern; a sensor configured to generate a signalthat represents the superimposed interference light pattern; and aprocessor configured to generate a dataset representative of the surfaceof the object.
 2. The intra-oral digitizer of claim 1 where theprojector comprises a hand-held intra-oral probe configured to bemanipulated in an oral cavity.
 3. The intra-oral digitizer of claim 2where the intra-oral probe projects the beam of structured light towardin vivo dentition and detects light reflected from the dentition.
 4. Theintra-oral digitizer of claim 1 where the reference arm generates atime-varying baseline pattern and the processor is configured togenerate the dataset according to time domain data processing.
 5. Theintra-oral digitizer of claim 1 where the signal generated by the sensorcomprises a shape, distribution and composition of the superimposedinterference light pattern.
 6. The intra-oral digitizer of claim 1 wherethe reference arm generates a fixed reference baseline pattern and thesensor comprises: a spectrometer configured to separate the superimposedinterference light pattern to constituent components; and a linearphotosensor configured to detect the constituent components.
 7. Theintra-oral digitizer of claim 1 where the processor is configured togenerate the dataset according to Fourier domain data processing.
 8. Theintra-oral digitizer claim 6 where the spectrometer comprises a grating.9. The intra-oral digitizer of claim 7 where the photosensor comprisesan array of light sensitive detectors.
 10. The intra-oral digitizer ofclaim 8 where the photosensor comprises a charge coupled device.
 11. Theintra-oral digitizer claim 1 where the light source comprises a beamsplitter configured to split the beam of structured light into a firstbeam and a second beam.
 12. An imaging system, comprising: a projectorconfigured to project a beam of structured light toward an object and todetect a reflection of at least a portion of the beam of structuredlight from the object; a coupler configured to generate a superimposedinterference pattern including the reflection and a baseline referencebeam of light, the baseline reference beam of light being based on thestructured beam of light; and a processor configured to generate adataset representative of a multi-dimensional visual image of the objectbased on the superimposed interference pattern.
 13. The imaging systemof claim 12 where the processor generates the dataset according totime-domain data processing.
 14. The imaging system of claim 12 wherethe processor generates the dataset according to Fourier-domain dataprocessing.
 15. The imaging system of claim 12 where themulti-dimensional image comprises a three-dimensional visualrepresentation of the object.
 16. The imaging system of claim 12 wherethe multi-dimensional image comprises a visually obscured portion of theobject.
 17. The imaging system of claim 16 where the object is a dentalitem.
 18. The imaging system of claim 17 where the obscured portioncomprises a margin.
 19. A method for generating a three-dimensionalvisual image of an in vivo object comprising: projecting a beam ofstructured light toward an object; detecting a reflection of at least aportion of the structured light from an exterior surface of the object;combining the reflection with a reference beam of light; determining amap of the surface of the object based on the combined reflection andreference beam.
 20. The method of claim 19 further comprising:projecting the beam of structured light toward an obscured surface ofthe object; detecting a reflection of at least a portion of thestructured light from the obscured surface of the object; combining thereflection of the structured light from the obscured surface with areference beam of light determining a map of the obscured surface of theobject based on the combined reflection and reference beam.